Incompatibility: Loading

by Don Friedman on October 12, 2016


New York tenements with changes of use at the first floor.

I’ve emphasized reuse a number of times. The phrase that you usually see is “adaptive reuse,” implying a change in occupancy, because ordinary reuse of buildings happens all the time and is rather boring. When a house is sold from one owner to another it is reused, but that means nothing to anyone but the people moving out and the people moving in.

Adaptive reuse usually involves alteration of some kind because the legal and practical requirements vary from one use to another. Apartment layouts, even for loft apartments, are different from factories and both are different from offices. New uses will require new partitions, new plumbing and electric services, and so on.

A number of years ago, we were hired by a restaurant located in an old tenement building. The restaurant proper was on the first floor, up a short stoop from the sidewalk, the catering department was on the second floor, and the two top floors were the offices, storage, and staff locker rooms. The business was thriving, but the landlord have never changed the Certificate of Occupancy from “multiple dwelling” to “commercial.” The restaurant owner was thinking about buying the building, but wanted the sale and use to be fully legal. There were a number of minor architectural and mechanical-systems issues that needed to be addressed, but the big one was load. The code (at that time, still similar today) required a live load of 100 psf for first-floor commercial use, 75 psf for upper-floor commercial use, and 50 psf for offices. The required load for a tenement was 40 psf in apartments and 100 psf in the public halls, but that was more or less meaningless because the floors in the building hadn’t been designed by an engineer. Wood joist floors in the 19th century were built using “rules of thumb” which is to say that the architect and builder used the same size joists they had used on the last successful project.

When we analyzed the floor joists, we had the good news that they were stronger than estimated. The bad news was that they were still not strong enough for the code-mandated loads needed to legalize the situation. We ended up reinforcing everything but the roof. By phasing the work, we only had to shut down one floor at a time, and the restaurant stayed open through the entire process.

Back to the point: the reuse was incompatible with the existing structure of the building. Because the reuse was otherwise logical, we upgraded the building until the incompatibility went away. Had the restaurateur known about this problem before he moved in, he probably would not have, and the building might well have been demolished.

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